title: Use of stroke distance in the early detection of simulated blood loss.
abstract: OBJECTIVE
  To compare the effects of simulated and mild actual hemorrhage on parameters used traditionally to assess hemorrhaging patients: heart rate (HR), blood pressure (BP), and Shock Index (SI = HR/systolic BP), with stroke distance (SD) measured ultrasonically as an index of cardiac stroke volume.
  
  
  METHODS
  Hemorrhage was simulated in 19 healthy volunteers by the application of graded lower-body negative pressure (LBNP) (0, -20, -40, and -60 mm Hg) to pool blood in the lower body and reduce venous return. Measurements were also made before and after a standard blood donation (450 mL) in nine healthy volunteers.
  
  
  RESULTS
  SD decreased significantly and progressively from the baseline level of 23.8+/-5.7 cm (mean+/-SD) at each level of LBNP: by 3.4+/-1.9, 7.4+/-2.5, and 11.8+/-3.2 cm at LBNP of -20, -40, and -60 mm Hg, respectively. Neither HR nor SI changed significantly at the lowest level of LBNP (-20 mm Hg), but they showed progressive, significant increases thereafter. Mean BP did not change significantly at any level of LBNP. Similarly, after a controlled hemorrhage of 450 mL, SD decreased significantly by 3.3+/-1.6 cm from 22.2+/-2.8 cm, whereas HR and SI remained unchanged and mean BP increased slightly.
  
  
  CONCLUSIONS
  Changes in SD may provide an earlier indication of progressive blood loss than either HR or BP alone or in combination.
authors.affiliation: Department Emergency Medicine, University of Manchester, England, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Hanson
authors.forename: R
authors.initials: R
authors.lastname: Van Hoeyweghen
authors.forename: E
authors.initials: E
authors.lastname: Kirkman
authors.forename: A
authors.initials: A
authors.lastname: Thomas
authors.forename: M A
authors.initials: MA
authors.lastname: Horan
mesh_terms: D000328:Adult; D001782:Blood Donors; D001794:Blood Pressure; D015150:Echocardiography, Doppler; D006339:Heart Rate; D006801:Humans; D016018:Least-Squares Analysis; D008150:Lower Body Negative Pressure; D008875:Middle Aged; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012771:Shock, Hemorrhagic / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013318:Stroke Volume; D013815:Thermodilution; D013997:Time Factors